Perform factorization as a last resort of unsafe fadd/fsub simplification.

Rules include:
  1)1 x*y +/- x*z => x*(y +/- z) 
    (the order of operands dosen't matter)

  2) y/x +/- z/x => (y +/- z)/x 

 The transformation is disabled if the new add/sub expr "y +/- z" is a 
denormal/naz/inifinity.

rdar://12911472

llvm-svn: 177088

1 files changed, 105 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/fast-math.ll b/llvm/test/Transforms/InstCombine/fast-math.ll
index 3e32a2e4dd4..47f1ec48046 100644
--- a/llvm/test/Transforms/InstCombine/fast-math.ll
+++ b/llvm/test/Transforms/InstCombine/fast-math.ll
@@ -350,3 +350,108 @@ define float @fdiv9(float %x) {
 ; CHECK: @fdiv9
 ; CHECK: fmul fast float %x, 5.000000e+00
 }
+
+; =========================================================================
+;
+;   Testing-cases about factorization
+;
+; =========================================================================
+; x*z + y*z => (x+y) * z
+define float @fact_mul1(float %x, float %y, float %z) {
+  %t1 = fmul fast float %x, %z
+  %t2 = fmul fast float %y, %z
+  %t3 = fadd fast float %t1, %t2
+  ret float %t3
+; CHECK: @fact_mul1
+; CHECK: fmul fast float %1, %z
+}
+
+; z*x + y*z => (x+y) * z
+define float @fact_mul2(float %x, float %y, float %z) {
+  %t1 = fmul fast float %z, %x
+  %t2 = fmul fast float %y, %z
+  %t3 = fsub fast float %t1, %t2
+  ret float %t3
+; CHECK: @fact_mul2
+; CHECK: fmul fast float %1, %z
+}
+
+; z*x - z*y => (x-y) * z
+define float @fact_mul3(float %x, float %y, float %z) {
+  %t2 = fmul fast float %z, %y
+  %t1 = fmul fast float %z, %x
+  %t3 = fsub fast float %t1, %t2
+  ret float %t3
+; CHECK: @fact_mul3
+; CHECK: fmul fast float %1, %z
+}
+
+; x*z - z*y => (x-y) * z
+define float @fact_mul4(float %x, float %y, float %z) {
+  %t1 = fmul fast float %x, %z
+  %t2 = fmul fast float %z, %y
+  %t3 = fsub fast float %t1, %t2
+  ret float %t3
+; CHECK: @fact_mul4
+; CHECK: fmul fast float %1, %z
+}
+
+; x/y + x/z, no xform
+define float @fact_div1(float %x, float %y, float %z) {
+  %t1 = fdiv fast float %x, %y
+  %t2 = fdiv fast float %x, %z
+  %t3 = fadd fast float %t1, %t2
+  ret float %t3
+; CHECK: fact_div1
+; CHECK: fadd fast float %t1, %t2
+}
+
+; x/y + z/x; no xform
+define float @fact_div2(float %x, float %y, float %z) {
+  %t1 = fdiv fast float %x, %y
+  %t2 = fdiv fast float %z, %x
+  %t3 = fadd fast float %t1, %t2
+  ret float %t3
+; CHECK: fact_div2
+; CHECK: fadd fast float %t1, %t2
+}
+
+; y/x + z/x => (y+z)/x
+define float @fact_div3(float %x, float %y, float %z) {
+  %t1 = fdiv fast float %y, %x
+  %t2 = fdiv fast float %z, %x
+  %t3 = fadd fast float %t1, %t2
+  ret float %t3
+; CHECK: fact_div3
+; CHECK: fdiv fast float %1, %x
+}
+
+; y/x - z/x => (y-z)/x
+define float @fact_div4(float %x, float %y, float %z) {
+  %t1 = fdiv fast float %y, %x
+  %t2 = fdiv fast float %z, %x
+  %t3 = fsub fast float %t1, %t2
+  ret float %t3
+; CHECK: fact_div4
+; CHECK: fdiv fast float %1, %x
+}
+
+; y/x - z/x => (y-z)/x is disabled if y-z is denormal.
+define float @fact_div5(float %x) {
+  %t1 = fdiv fast float 0x3810000000000000, %x
+  %t2 = fdiv fast float 0x3800000000000000, %x
+  %t3 = fadd fast float %t1, %t2
+  ret float %t3
+; CHECK: fact_div5
+; CHECK: fdiv fast float 0x3818000000000000, %x
+}
+
+; y/x - z/x => (y-z)/x is disabled if y-z is denormal.
+define float @fact_div6(float %x) {
+  %t1 = fdiv fast float 0x3810000000000000, %x
+  %t2 = fdiv fast float 0x3800000000000000, %x
+  %t3 = fsub fast float %t1, %t2
+  ret float %t3
+; CHECK: fact_div6
+; CHECK: %t3 = fsub fast float %t1, %t2
+}